Electric lamp



April 18, 1944. v w M JOHNSQN 2,347,055

ELECTRIC LAMP Filed Jan. 6,. 1943 PEI;

Inventor: WiLber" M. Johnson,

b8 WM His A'FEOYne Patented Apr. 18, 1 944 l v 2,347,05s

ELECTRIC LAMP.

Wilber M. Johnson, Cleveland Heights, Ohio, assignor to General ElectricCompany, a corporation of New York Application January 6, 1943, SerialNo. 471,467

3 Claims.

My invention relates to electric lamps of the type comprising anenclosure for a light source, which enclosure is filled with gas, suchas air.

A type of lamp in conjunction with which my invention is useful is knownas a "Sealed Beam lamp and is now in extensive use in automobileheadlights. One type of such lamp comprises a small electricincandescent lamp mounted within an enclosure having a reflector portionof paraboloidal or other suitable shape and a lens or cover portionsecured at its periphery to the reflector portion to form an enclosure.The base of the incandescent lamp extends through the reflector portionand the enclosure is filled with air. Such lamps tend to breathe; thatis, the air flows in and out of it, if the enclosure is not air=tight,since the enclosed. air expands and contracts as the temperature of thelamp rises' and falls. The air from the outside atmosphere entering thelamp enclosure under such conditions may be and usually is mixed withundesired and even harmful substances, such as water vapor whichcondenses on the inner surface of the enclosure and changes the patternof the projected beam, or sulphur or other gaseous vapors which impairthe surface of the reflector. In order to prevent such breathing action,it has heretofore been the practice to make the joint between the coverand the reflector and that between the reflector and the base of thelamp gas tight and oi substantial mechanical strength to withstand theincreased pressure of the air in the enclosure when the temperature israised by operation of the lamp, by the heating action of the sun or byheat from other sources.

The principal object of my invention is to provide a lamp of the abovetype which may breathe without being contaminated by material from theoutside atmosphere. Another object of my invention is to reduce themanufacturing cost of such lamps. Further objects and advantages of myinvention will appear from the following description thereof.

It is well known that gas tight seals of large mechanicalstrength aremore difiicult and expensive to make than such seals of small mechanicalstrength. Further, in the fabrication of gas tight seals there is acertain amount of wastage or spoilage due to a portion of the seal beingtoo weak mechanically to withstand the variations in gas pressureencountered under service conditions. According to my invention thehermetic seals of such lamps may be of small mechanical strength and incertain instances gas pervious, mechanical joints may be substituted forgas tight joints without harmful material from the outside atmosphereentering the lamp enclosure to the end that the cost of manufacture ofsuch lamps is substantially reduced. Whereas prior efiorts have been inthe direction of increasing the mechanical strength of the lampenclosure to withstand increasing gas pressure and thus resisting thetendency of the lamp enclosure to breathe I proceed in the oppositedirection to solve the common problem in a less expensive ,manner bypermitting the lamp enclosure to breathe and thus avoid pressure changeswith changes in temperature.- Instead of keeping the volume of theenclosure constant, which causes the pressure to change directly withthe temperature, I provide means whereby the volume of the enclosure maychange as the gas expands and contracts with changing temperature. Thegas in the enclosure is then at atmospheric pressure under temperatureconditions encountered in service which eliminates mechanical stressfrom this source on the seals. In accordance with my invention, thejoints may be made, of lesser mechanical strength and thus with lessexpense by providing an easily collapsible and expansible pocket orchamber communi cating with the interior of the reflector lamp. In oneembodiment of my invention the joint between the reflector and the lampbase may be pervious to air, thus eliminating one of the expensivehermetic joints or seals used heretofore.

In the drawing accompanying and forming part of this specificationspecies of my invention are shown in conjunction with a Sealed Beam lampof, a type well known in commerce. Fig. 1 of the drawing is a sidelevational, partly sectional View of the lamp, an electrical supplyterminal therefor and an easily collapsible and expansible sleevecommunicatin with the interior of the lamp; Fig. 2 is a fragmentary,partly sectional view of a similar lamp having an easily collapsible andexpansible bag communicating with the interior thereof through a pipe orconduit, and Fig. 3 is a similar view of a bag similar to that shown inFig. 2 communicating with the interior of the lamp through an orifice.Like numbers denote like parts in all theiigures.

Referring to Fig. 1 of the drawinathe lamp lfi comprises a reflector"member II of, paraboloidal shape having a flange l2 rolled over onto theouter surface of the peripheral portion of a lens I3. A gasket I4 offlexible, air impervious material, such as rubber, is interposed betweenthe reflector H and the lens l3 and is compressed therebetween to forman air-tight or hermetic seal between the reflector II and the lens I3.In some types of commercial lainps the reflector II, the lens I3 and thegasket III are held together by a clamping ring. A smallincandescent-lamp I5 is mounted in the space defined by the reflector IIand the lens I3 and is supported therein by its metal base I6 whichextends through an opening in the apex of the reflector II and which issoldered to the reflector II. The incandescent lamp I5 may be of thetype disclosed and claimed in the Severin Patent No. 2,227,324, issuedDecember 31, 1940, and assigned to the assignee of this application andwhich comprises, in addition to the base I5, a glass bulb I! having aneck portion extending into the base I 6 and secured thereto by basingcement. The lamp I5 has a pair of filaments supported in the bulb I"! bycurrent in-leads which pass through the stem of the bulb I1 and connectwith spaced contacts I8 on the base I6 of the lamp I5. The filaments,the stem and the in-leads of the lamp I5 have been omitted from thedrawing for purposes of simplicity of illustration. A connector memberl9 fastened to the end of a current or power supply cable 20 engageswith the terminals I8 of the lamp I5 in the usual manner.

The lamp I described above is well known in commerce and the abovedescribed structure constitutes no part of my invention.

As pointed out above, 'prior efforts have been in the direction ofmaking the lamp I0 air-tight to prevent the ingress of contaminating,deleterious material into the lamp enclosure. Thus, the space betweenthe base I and the reflector II has been filled with solder to make thejoint therebetween air-tight or hermetic at pressures above and belowatmospheric pressure and a special composition impervious to air hasbeen used to seal the space between the base I6 and the bulb I! for thesame purpose, all as disclosed in copending application Serial No.385,672, filed March 28, 1941, and assigned to the assignee of thisapplication. Such precautions and special procedures add to the cost ofmanufacture of the lamps and are eliminated by my invention whichcomprises, in the embodiment thereof illustrated in Fig. 1, an easilycollapsible and expansible sleeve 2| of material impervious to air, suchas soft rubber, oiled silk, or the like, surrounding the member I9 andthe portion of the lamp base I6 outside the reflector I I. The sleeve 2|is provided with two rings 22 of flexible material, such as soft rubber.The rings 22 are of such diameter that they are stretched and undertension when mounted on the cable 20 and on the flange 23 on thereflector II. The flange 23 is integral with the reflector II andprovides an annular groove 2|, one of the rings 22 is stretchedsufliciently to pass the member I9 into the sleeve 2|. The opposite ring22 is then stretched to permit the engagement of the member IS with thecontacts I8 and thereafter the ring 22 is placed in the groove formed bythe flange 23. The rings 22 grip the cable 20 and the surface of thegroove with sufficient force to prevent seepage of air from the ambientinto the sleeve 2| under the conditions described below.

It is advantageous in the practice of my invention to provide a lowresistance path for the flow of air between the interior of the lamp I0and the interior of the sleeve 2|. The building up of pressure in thelamp I0 and concomitant stress on the gasket I 4 is thus avoided.Accordingly, instead of filling the annular space between refor one ofthe rings 22. In mounting the sleeve flector I I and the base It of thelamp I5 with solder as has been the practice heretofore, in an effort toseal this space, only sufliclent solder is used to support the lamp I5in the reflector II without sealing the said space. I prefer to solderthe base I5 to the reflector II at three spaced places around the baseI6 so as to leave spaces between said base I6 and said reflector II forthe free flow of air between the lamp I0 and the sleeve 2|. Thus, whenthe lamp I0 is at the temperature of the ambient and the sleeve 2| iscollapsed, air flows freely from the lamp I0 into the sleeve 2| as thetemperature of the lamp I0 increases and the air therein expands whenthe lamp I5 is energized. The sleeve 2| expands as the air from the lampI0 enters it. When the lamp I5 is deenergized and the reflector lamp I0cools, the air therein contracts. The uncontaminated air from the sleeve2| then flows back into the lamp III through the mechanical jointbetween the reflector II and the base I8 and the sleeve 2| collapses.The above cycle is repeated each time the temperature of the lamp I0rises above and then falls to the temperature of its surroundings.

It is apparent from the foregoing that the difference in the airpressure inside and outside the lamp I0 is inappreciable at all times,that the expensive air-tight seal between the lamp base I6 and thereflector II as well as that between the lamp bulb I1 and the base I6have been eliminated and that the mechanical stress on the seal betweenthe reflector I and the cover I3 has been minimized while the ingress ofcontamination from the ambient into the lamp I0 is prevented by mystructure, Further, the sleeve 2| is easily detachable from the lamp I0and attached to a new lam-p when lamp replacement is necessary.

The embodiment of my invention illustrated in Fig. 2 of the drawingcomprises an easily collapsible and expansible bag 24 which isimpervious to air and which has a neck portion 25 which grips theenlarged end portion 26 of a tubular extension 2'! on the reflector Thebag 24 may consist of soft rubber, oiled silk, or similar material, andthe neck portion 25 thereof ,may consist of soft rubber or othermaterial capable of gripping the end portion 25 of the extension 21.This embodiment of my invention is particularly useful in conjunctionwith lamps made in the conventional manner, that is, with the spacebetween the base Hi and the reflector sealed with solder as shown at 28.While a special sealing composition may be used to make the spacebetween the base I6 and the bulb I'I air-tight in accor dance with theapplication referred to above, I prefer to omit such composition andthus save its cost when using this embodiment of my invention. This maybe done Without risk of contamination from the ambient entering the lampII) because the usual basing cement offers appreciable resistance to theflow of air between the base I6 and the bulb I'I whereas the resistanceto the flow of air through extension 21 between the lamp l0 and the bag24 is inappreciable. Thus, as the air in lamp I0 expands with increasingtemperature, it flows from lamp I0 into the bag 24. The sameuncontaminated air flows back into lamp II] when the air contracts whenthe lamp temperature falls. In this embodiment as in the embodimentillustrated in Fig. 1, the building up of pressure in the lamp It] withits accompanying stress on the seals is avoided without permittingcontamination to enter lamp I0 pressures.

The embodiment of the invention illustrated in Fig. 3 is the same asthat illustrated in Fig. 2 except that the bag 24 is provided with aring 29 which is similar to rings 22 illustrated in Fig. l

and which clamps :about an annular groove formed by a circular,outwardly flaring flange 30 on the reflector H and about the opening 3|in said reflector H. This is a more compact arrangement than that shownin Fig. 2 and may be preferred where mounting space for lamp III issmall.

In the species of my invention illustrated in Figs. 2 and 3 of thedrawing, the easily collapsible and expansible member is mounted only onthe replaceable lamp in per se and not on the permanent parts oftheinstallation or vehicle. When the lamps are to be placed in stock for atime before being used, these embodiments may be preferred since the bag24 may be placed thereon to serve the same purposes as it I0 is in use.

In order to eliminate moisture or water vapor in the lamp In it may beflushedwith dry air and a getter, such as calcium chloride, may bedisposed in the sleeve 2 I, the bag 2, the conduit 21, or on the memberl9. Under certain service conditions it may be desirable to use both thesleeve 2| and the bag 24 on a single lamp for attaining the objects andadvantages of my invention.

While I have illustrated and described my invention in conjunction withheadlamps of a commercial type for vehicles, I contemplate that it maybe used with other types of lamps and with lamps used for otherpurposes. Further, electrical conductors in the form of metal wires orrods may be used for passing energy into the lamp instead of a lampbase.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

l. A lighting unit comprising an enclosure including a reflector, and anelectric lamp in said enclosure, said enclosure containing a gaseousatmosphere and being normally air-tight but sub- :Iect to leakagethrough a portion thereof upon does when the lamp expansion andcontraction oi the internal atmosphere when the lamp is turned on andoff, and an air-tight easily collapsible and expansible baglike memberconnected with the interior of said enclosure, said bag-like memberhaving suflicient volume to accommodate the internal atmosphere which isexpanded when the lamp is lighted and to prevent a rise in pressuresuflicient to cause the internal atmosphere to leak out of the enclosureto the exterior atmosphere, the internal atmosphere in said member beingreturned to the enclosure when the unit cools.

2. A lighting unit comprising an' enclosure including a concavereflector and a cover glass sealed together at their peripheries, and anelectric lamp mounted in an opening in said reflector, said enclosurecontaining a gaseous atmosphere and being normally air-tight but subjectto leakage through said opening upon expansion and contraction of theinternal atmosphere when the lamp is turned on and oif, a detachablecurrent supply connector at the exterior of said enclosure engagingterminals on said lamp, and an airtight easily collapsible andexpansible bag-like member engaging the reflector around the saidopening therein and enclosing the said connector, said bag-like memberhaving sufficient volume to accommodate the internal atmosphere which isexpanded when the lamp is lighted and returning the atmosphere pocketedtherein to the enclosure when the unit cools.

3. A lighting unit comprising anenclosure including a concave reflectorand a cover glass sealed together at their peripheries, and an electriclamp in said enclosure comprising a bulb and a base, said lamp basebeing mounted in an opening in said reflector and hermetically sealed tothe margin of said opening, said enclosure containing a gaseousatmosphere and being normally air-tight but subject to leakage throughthe interior oi the said lamp base, and an air-tight easily collapsibleand expansible bag-like member connected with the enclosure through anopening in said reflector, said bag-like member having suilicient volumeto accommodate the internal atmosphere which is expanded when the lampis lighted and to prevent a rise in pressure suflicient to cause theinternal atmosphere to leak through the lamp base to the exterioratmosphere, the internal atmosphere in said member being returned to theenclosure when the unit cools.

WILBER M. JOHNSON.

